The EPO's Enlarged Board Prepares to Tackle Claim Interpretation and Added Matter

The Dispute That Triggered the Referral 

The appeal in T 873/24 turns on a single claim feature: a ratio of titanium to nitrogen stated as "in excess of 3.42." The claim does not specify whether this is a weight ratio or a molar ratio. 

• The patent proprietor's position was that reading the claim alongside the description, the skilled person would understand the ratio to be by weight. The original application supports a weight-ratio reading, so no added matter arises. 
• The opponent's position was that the claim, taken on its face, encompasses both interpretations. Because only the weight ratio has basis in the original filing, permitting a molar-ratio reading means claim 1 covers something not disclosed in the application as filed — a classic Article 123(2) violation. 

Board 3.3.05 concluded that the outcome hinges entirely on how the specification is "consulted." It identified three lines of authority, each producing a different result for the assessment of Article 123(2) EPC in the case at hand. 

Three Competing Interpretive Frameworks 

Framework A — Minimal Specification Input 

The description serves only to identify who the skilled person is and what they know generally. Beyond that, every technically coherent reading of the claim is in play. Decisions in this camp include T 618/23, T 412/24, T 2047/23 and T 837/24. T 412/24 is the clearest example: there the Board consulted the description solely to define the skilled reader, holding that a sensible claim construction cannot be reinterpreted merely because the description has been “consulted” or “referred to.” 

Framework A applied to the referred case would imply that both weight and molar ratios are in principle possible; the claim therefore fails Article 123(2) because the molar interpretation lacks original support. 

Framework B — Context-Aware, But No Importation 

The specification provides technical context that can be used to rule out readings that would be incompatible with the invention's subject-matter. However, limitations appearing only in the description cannot be used to interpret the scope of claim terms; nor can the interpretation of a broad term be artificially narrowed when it conveys clear technical teaching on its own. This is the most popular position of the boards as reflected in T 873/23, T 981/23, T 1071/23, T 2001/23, T 2488/22, T 235/25, T 1052/23, T 1973/23 and T 1164/23. The turntable-ladder case T 2027/23 (IVECO) is the cleanest illustration: the Board refused to read “computer,” “electrical signal” and “real-time” limitations drawn from the embodiments in the application to limit the broader claim terms, warning of the “Angora cat” risk of a claim presented narrowly in prosecution and broadly in litigation. The proper remedy for a discrepancy between claim and description, the Board held, is amendment by the patentee — not “interpretative somersaults” by the Board. 

Framework B applied to the referred case would imply that the description cannot inject a "weight ratio" limitation into the claim. The result mirrors Framework A — added matter is present. 

Framework C — Holistic, Unified Construction 

Claim interpretation is a single exercise: the skilled reader absorbs the entire patent document and assigns meaning to the terms of the claims accordingly. This aligns more closely with the approach taken by the Unified Patent Court. Boards following this line of reasoning include T 2048/22, T 727/23, T 847/24, T 2067/22 and — notably — T 439/22, the very decision on the case that produced G 1/24. There the Board treated the reading of claims and the consultation of the description and drawings as a single, unitary process and allowed a definition present in the description to govern the meaning of “gathered sheet.” Thus, the Board that generated G 1/24 itself applied the holistic approach, while other Boards have since gravitated toward the more restrictive Frameworks A and B. 

Framework C applied to the referred case would imply: A skilled reader of the complete specification would understand "ratio" to mean weight ratio. Under this view, no added matter exists. Thus, in practice, only Framework C would require you to interpret the terms of the claims based on what is taught in the description. 

The Questions Put to the Enlarged Board (rephrased) 

Procedural Admissibility (Question 1) 

This relates more to whether or not the Enlarged Board of Appeal can consider the questions referred to it and is not related to the substantive argument. Article 112(1) EPC allows a referral to the Enlarged Board of Appeal only when it is "required" for uniform application of the law or when a fundamental legal issue arises. Case law has further refined this to require that the question must be outcome-determinative in the referring case. Board 3.3.05 itself considers that standard impractical and asks the Enlarged Board to clarify whether a referral is admissible if the legal issue genuinely arises in the pending proceedings and it is reasonable for the Board to address it — even if not strictly decisive. 

Scope of Specification-Based Interpretation (Questions 2a and 2b) 

These questions relate to the influence of the description on the interpretation of the claims: 

• 2(a): Does treating claims as the "starting point and basis" for patentability preclude reading features/definitions present only in the description into claim terms — especially where doing so would restrict their meaning? 
• 2(b): If this is allowed, is claim interpretation a unified process combining claim language with the full specification, and does this imply that only interpretations of the claims that plainly contradict the skilled reader's general technical understanding are excluded?  

Added-Matter Consequences (Questions 3a and 3b) 

• 3(a): When testing compliance with Article 123(2) EPC, must every technically sensible reading of the claim (viewed in isolation) find support in the original filing? 
• 3(b): If not, is it enough that the interpretations derived from the specification as a whole are directly and unambiguously disclosed in the application as filed? 

What Happens in the Meantime? 

The EPO President has confirmed that examination and opposition proceedings will continue normally while G 1/26 is pending — disruption to the system would undermine legal certainty. A decision is not expected before 2027. 

How the Boards Handle Added Matter 

Most Boards have already settled on a two-step method for Article 123(2) EPC. Step 1 interprets the claim and Step 2 then tests the claim as interpreted against the “gold standard” — whether the subject-matter is directly and unambiguously derivable from the application as filed. The split in outcomes thus arises almost entirely at Step 1, from how far the description is allowed to colour the claim. 

Several decisions demonstrate how the reading of G1/24 can affect added matter. In T 405/24 the argument that where several technically sensible readings exist, one may simply adopt the description-supported reading to ensure compliance was rejected. The Board warned that this would mean virtually no Article 123(2) violation could ever arise, and held that all technically reasonable interpretations must be taken into account. In T 1071/23  the Board argued that G 1/24 cannot rescue a technically unfeasible, undisclosed feature. By contrast, T 2048/22 shows G 1/24 helping the patentee, using the description to confirm that “co-aligned” and “common” pores were synonymous and thus also disclosed in the application as filed.  In T117/23 the Board argued that G 1/24 indicates that not in all cases definitions or meanings of the terms that may be implied by the description must necessarily be adopted (referring also to T 1561/23) but emphasized that the assessment will depend on the circumstances of the case at hand.  

Connection with G 1/25 

G 1/24 and G1/26 are also relevant for the parallel pending referral G 1/25 (from T 697/22), which asks whether the description must be adapted to bring it into line with claims amended in opposition or appeal, and on what legal basis. G 1/24’s instruction to always consult the description implies that to a certain extent (depending on the outcome of G1/26) amendments made to the description may affect the interpretation of the claims. The Enlarged Board issued a preliminary opinion in G 1/25 on 11 March 2026 leaning toward requiring adaptation under Article 84 EPC, with oral proceedings held in May 2026 and a written decision awaited. 

Practical Significance 

Claim wording frequently determines the fate of a patent in examination, opposition, or litigation. G 1/26 will thus affect both the scope of protection and how claim interpretation can affect added-matter issues. In the meantime applicants, patentees, and opponents must aim to deal with quite opposing potential outcomes. 

Some concrete precautions appear advisable. When drafting and prosecuting, keep claims and description consistent to avoid unintended readings; do not rely on a definition in the description to narrow an otherwise broad claim term, since a narrower description definition will not necessarily override a clear, broader claim word; and avoid definitions that conflict with the established meaning of a term. Adapting the description to the allowed claims should always be done carefully taking into account potential impact on the scope of the claims.  Fallback positions which allow amendment in case of discussion should always be envisaged. 

For opponents, the description and drawings are a source of ammunition: search them for broadening definitions or embodiments that support a wider claim reading capturing the prior art, resist the patentee’s attempts to narrow clear claim terms by reference to embodiments in the description, and make use of claim/description inconsistencies.  

De Clercq & Partners is happy to assist you in determining whether these decisions may affect your pending cases and how to best prepare for any potential outcome of G1/26. Please do not hesitate to contact us at info@dcp-ip.com.